Smooth vertices along on a curved mesh
You have the LoopTools &gt; Curve that allows you to curve a series of vertices: select the 2 extremities + a vertex somewhere between the 2, and right click &gt; LoopTools &gt; Curve. But you can't control the curve shape afterwards, the central vertex position gives the curve shape (of course another way would be to align the vertices then move up one of them with the Proportional Editing on).